Drilling a well to produce hydrocarbons typically involves the use of well tubulars, such as casing, tubing, drill pipe or drill collars. Occasionally, such well tubulars become stuck downhole and a “back off” procedure is performed. Typically, such a procedure involves the use of an explosive device, such as a “string shot tool.” A conventional string shot tool uses a measured length of detonating cord (a secondary explosive available in a rope-like form) to provide explosively generated concussion (shock) to a tubular connection allowing that connection to be decoupled, the connection torque released, and the pipe above to be recovered from the depth of the string shot.
Conventionally, a string shot tool also requires an explosive initiator for ignition. The initiator can contain primary or secondary explosives and may be qualified as Radio Frequency (RF) Safe, Stray Voltage (SV) Safe or a RF-SV safe initiator. Explosives are often regulated and controlled and require special procedures for import, storage, transport and handling in many countries.